1. Field of the Invention
This invention relates to a triazinethiol-containing anticorrosive coatings, anticorrosion treatment method, and anticorrosion-treated metal material, and, more specifically, to a non-chromium anticorrosive coating with superior anticorrosion ability to that of known chromium-containing anticorrosion agents, to a corresponding anticorrosion treatment method, and to a corresponding anticorrosion-treated metal material.
2. Description of the Related Arts
When zinc coated steel plate or alloyed zinc coated steel plate are exposed to an atmosphere containing saline or brine, or are exposed to high temperature and high humidity, white rust forms on the surface. This white rust greatly damages both the outward appearance and the ability to prevent corrosion of the base iron surface.
To prevent white rust, chromium based anticorrosion agents are widely used. For example, Japanese Laid-open Publication No. Hei 3-131370 discloses a resin type treatment agent wherein a water dispersible chromium compound and water dispersible silica are incorporated in an olefin-.alpha., .beta.-ethylenic unsaturated carboxylic acid polymer resin dispersion.
However, even this type of chromium-containing resin type treatment agent does not necessarily have sufficient anticorrosion properties, and, if exposed to brine or to a high temperature and high humidity atmosphere for an extended time, white rust forms even when this treatment agent is used. Also, it has recently been understood that chromium is highly toxic, and consequently the use of chromium on equipment or in places where coated objects come in direct contact with workers has been limited.
The demand for non-chromium anticorrosion treatment agents has therefore been increasing, leading the inventors in the present application to find that sulfide ion reacts with zinc so as to form a stable ZnS coating, and their invention of a non-chromium anticorrosion treatment agent using sulfides and sulfur, as dislosed in Japanese Laid-open Publication No. Hei 8-239776 and Japanese Laid-open Publication No. Hei 8-67834.
However some sulfides emit a peculiar odor, and their handling is not always easy.
An anticorrosion treatment agent using a triazinethiol compound containing sulfur atoms, and without any foul odor or toxicity, has also been proposed. For example, the "water-soluble anticorrosion coating" of Japanese Laid-open Publication No. Sho 53-31737 discloses a water-soluble anticorrosion coating to which a dithiol-S-triazine derivative is added.
Also, the "metal-reactive emulsion" of Japanese Laid-open Publication No. Sho 61-223062 discloses a metal-reactive emulsion obtained by mixing a triazinethiol compound with an organic compound that is difficultly soluble or insoluble in water.
However the water-soluble anticorrosion coating disclosed in Japanese Laid-open Publication No. Sho 53-31737 is intended to prevent corrosion of soft steel, copper, brass, or copper wire, and is prepared in order to adsorb particularly well to a base material of copper or brass. This agent is therefore inadequate as an anticorrosion agent for zinc or other metal surfaces. Also, the reactive emulsion disclosed by Japanese Laid-open Publication No. Sho 61-223062 reacts with copper, nickel, tin, cobalt, aluminum, and their alloys, and was inadequate as an anti-corrosion agent for zinc and other metal surfaces.